VMS Help Sys Parameters, TMSCP_SERVE_ALL  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    TMSCP_SERVE_ALL is a bit mask that controls the serving of tapes.
    The settings take effect when the system boots. You cannot change
    the settings when the system is running.

    Starting with OpenVMS Version 7.2, the serving types are
    implemented as a bit mask. To specify the type of serving your
    system will perform, locate the type you want in the following
    table and specify its value. For some systems, you may want
    to specify two serving types, such as serving all tapes except
    those whose allocation class does not match. To specify such a
    combination, add the values of each type, and specify the sum.

    In a mixed-version cluster that includes any systems running
    OpenVMS Version 7.1-x or earlier, serving all available tapes
    is restricted to serving all tapes except those whose allocation
    class does not match the system's allocation class (pre-Version
    7.2 meaning). To specify this type of serving, use the value 9,
    which sets bit 0 and bit 3. The following table describes the
    serving type controlled by each bit and its decimal value.

           Value
           When
    Bit    Set     Description

    Bit 0  1       Serve all available tapes (locally attached and
                   those connected to HSx and DSSI controllers).
                   Tapes with allocation classes that differ from the
                   system's allocation class (set by the ALLOCLASS
                   parameter) are also served if bit 3 is not set.
    Bit 1  2       Serve locally attached (non-HSx and non-DSSI)
                   tapes.
    Bit 2  N/A     Reserved.
    Bit 3  8       Restrict the serving specified by bit 0. All tapes
                   except those with allocation classes that differ
                   from the system's allocation class (set by the
                   ALLOCLASS parameter) are served.

                   This is pre-Version 7.2 behavior. If your cluster
                   includes systems running OpenVMS Version 7.1-x
                   or earlier, and you want to serve all available
                   tapes, you must specify 9, the result of setting
                   this bit and bit 0.

    Although the serving types are now implemented as a bit mask, the
    values of 0, 1, and 2, specified by bit 0 and bit 1, retain their
    original meanings:

    o  0 - Do not serve any tapes (the default for earlier versions
       of OpenVMS).

    o  1 - Serve all available tapes.

    o  2 - Serve only locally attached (non-HSx and non-DSSI) tapes.

    If the TMSCP_LOAD system parameter is 0, TMSCP_SERVE_ALL is
    ignored.